Tienen, por eso no lloran,
de plomo las calaveras.
Con el alma de charol
vienen por la carretera.
[Their skulls are lead--that's why they don't weep. With souls of patent leather come over the highway]
This de-humanizing moment comes toward the beginning of Lorca's "Romance de la guardia civil española." "Charol" is the material that famous tricornio hats is made of, so the souls of the guardia civil is made of the same material. The metonymy is made into a metaphor.
The guardia civil was founded in the late 19th century to patrol rural roads. It is a completely militarized police force, with a reputation for brutality. Since the gypsies were an itinerant, marginalized group, they were the natural target of this paramilitary force. In this poem they attack a gypsy settlement while the gypsies are putting on some kind of Christmas party. There are children dressed up as the Virgin and Saint Joseph. There is someone dressed up as Pedro Domecq, the local oligarch, here near the Southern Andalusian city of Jerez de la Frontera. (Detrás va Pedro Domecq / con tres sultanes de Persia.) You've probably drunk his products. ("Sherry" is how a British guy pronounces "Jerez.")
So it is the destruction of pure innocent imagination by pure depravity. There is no middle ground. The guardia civil went enthusiastically for the right during the civil war.
What's the Pope going to dress up in next?